Recently, there has been proposed a device that forms a predetermined light distribution pattern by reflecting the light emitted from a light source to the front of a vehicle and scanning the region in front of the vehicle with the reflected light. For example, there has been proposed an optical unit including a rotary reflector that rotates in one direction around a rotation axis while reflecting light emitted from a light source, and a plurality of light sources including light-emitting elements. The rotary reflector is provided with a reflective surface such that a desired light distribution pattern is formed by the light of the light source reflected by the rotary reflector while the rotary reflector is rotated (see, e.g., Japanese Patent Laid-Open Publication No. 2015-026628).